Contact block for rotary potentiometers



July 7, 1970 A, s; LQUIS ET AL 3,519,973

CONTACT BLOCK FOR ROTARY POTENTIOMETERS Filed July '7, 1967 2 Sheets-Sheet l July 7, 1970 A. s. Louis ETAI- 3,519,973

`CONTACT BLOCK FOR ROTARY POTENTIOMETERS 2 Sheets-Sheet 2 Filed July 7, 196'? United States Patent O 3,519,973 CONTACT BLCK FOR ROTARY PGTENTIOMETERS Arnold S. Louis, Hastings-on-Hudson, N.Y., and S. Frederic Guggenheim, Teaneck, NJ., assignors to Markite Corporation, New York, N.Y., a corporation Filed July 7, 1967, Ser. No. 651,892 Int. Cl. H01c 5 /02 U.S. Cl. 338-162 12 Claims ABSTRACT F THE DISCLOSURE A contact block for rotary potentiometers and the method of manufacturing same, including a hub portion insulatingly supporting, with respect to one another, a plurality of wing-like sections on each of which may be carried a conductive contact member intended to engage a resistive track provided on the interior of the potentiometer casing. Each wing-like section comprises an assembly of two wing-like plates between which is sandwiched the conductive contact member for slidable movement therebetween. A third intermediate plate section is located between each pair of plates to provide an inner guide rail for the slidable movement of the conductive contact member while overlapping tab members of one of the exterior plates defines an outer guide rail for the movement of the conductive contact member. During manufacture the plates of the contact assembly are integrally formed with removable perimeter portions `which may be detached after the molding of the hub portion such that the winglike plate sections remain insulatingly imbedded with respect to one another in the thus formed hub portion.

This invention relates to potentiometers and more particularly to contact blocks for rotary potentiometers, and the method of manufacturing same.

Rotary potentiometers are well known in the art and generally include a casing within the interior of which is secured a resistive track to which potential may be applied. The casing carries a shaft rotatably supported therein, and rigidly secured to the shaft for rotation therewith is provided some type of contact block carrying one or more conductive contact members which engage the resistive track provided on the interior of the casing. An electrical circuit is provided from the conductive contact member to a terminal on the exterior of the casing, whereby dependent upon the location of the conductive contact member on the resistive track, a predetermined proportion of the voltage applied to the resistive track may be taken oil the external terminal.

Contact blocks for rotary potentiometers of the prior art have many disadvantages which the instant invention effectively overcomes. Specifically, when it is desired to utilize a plurality of conductive contact members on a contact block, such that a plurality of waveforms may be taken off the single potentiometer, it is imperative that each of these conductive contact members be insulatingly supported with respect to one another on the contact block to which they are secured. In this manner individual circuit paths may be provided from the respective conductive contact members to respective ones of a plurality of external terminals. To effectuate the insulative mounting of the individual conductive contact members, the prior art has suggested individually and permanently securing the conductive contact members to a disc of insulating material which is mounted on the rotating shaft of the potentiometer.

Although a cumbersome and rather expensive method, the prior art technique of permanently securing the plu- 3,519,973 Patented July 7, 1970 ICC rality of conductive contact members to the insulative disc, accomplishes the broad objective of insulating the conductive contact members from one another but gives rise to another more serious problem. Specifically, after the contact block and shaft are inserted into the interior of the potentiometer casing such that the conductive contact members are in engagement with the resistive track, it is customary to adjust or phase the conductive contact members relative to one another. For instance, if it is desirable to provide a sine, cosine potentiometer, two conductive contact members are required, with each being separated by Furthermore, whether such conductive contact members are exactly 90 out of phase, can only be determined after the contact block has been inserted in the potentiometer such that the conductive contact members are in engagement with the resistive track and measuring apparatus, such as an oscilloscope can be connected to the external terminals. However, with the prior art contact blocks described above, wherein the conductive contact members have been permanently secured to the insulative discs, the contact members cannot be moved relative to one another on the resistive track. Thus the initial uncalibrated placement of the conductive contact members is a linal placement which frequently gives rise to outputs which are not properly phased with one another.

One further shortcoming of potentiometer rotary contact blocks of the prior art is the diiculty encountered when it is desirable to gang a plurality of such contact blocks on a single shaft to increase and vary the type of outputs the potentiometer is capable of delivering. Thus the rather irregular and unwieldly shapes and designs of the various components of the prior art contact blocks do not lend themselves to being assembled in the ganged relationship within a single potentiometer casing.

ln contradistinction to the prior art, the instant invention provides a relative simple, inexpensive and compact contact block for use in a rotary potentiometer which insulatingly maintains a plurality of conductive contact members with respect to one another, makes possible final calibration (phasing) of the conductive contact members after the contact block has been inserted within the potentiometer casing, and which is of such configuration as to lend itself to multiple ganged assemblies whereby many varied output signals may be inexpensively provided from a single potentiometer.

In its preferred embodiment the contact block of the instant invention includes a central hub portion of insulating material within which are supported a plurality of wing-like sections in insulating relationship with respect to one another. One or more of the wing-like sections carries a conductive contact member which engages the resistive track of the potentiometer when the rotary contact block is inserted in the potentiometer casing. An electrical circuit path is provided from the conductive contact members to a conductive ring carried by the hub portion, which ring forms part of a circuit path to the exterior of the casing. As will be explained in greater detail, the individual wing-like sections carried by the hub portion of the contact block, actually comprise an assembly of three plate sections so arranged as to provide a track within which the conductive contact members are slidably received during the initial stages of manufacture.

In accordance with teachings of the instant invention, after the contact block is inserted in the potentiometer casing such that the conductive contact members are in engagement with the resistive track, it is possible, to physically displace the conductive contact members relative to one another such that they may be properly and accurately phased to give the desired electrical output. It is only after the proper phasing has been selected, that the conductive contact members are permanently secured in place on the respective wing-like sections.

In accordance with a particularly advantageous feature of the instant invention, and as will be described in greater detail, a unique method is provided for manufacturing the above described contact blocks. Specifically a plurality of plates are formed each having a perimeter portion and a plurality of inwardly extending plate-like sections. The plates are aligned relative to one another and the hub portion of the contact block is molded about the central portion of the plate-like sections. Finally, the perimeter portions of the plates are removed, leaving the above described `plurality of wing-like sections imbedded in the hub after which the conductive contact members may be added thereto.

Accordingly, it is an object of the instant invention to provide a contact block for a rotary potentiometer which includes a hub of insulating material about which is disposed a contact assembly comprising a plurality of wing-like sections insulatingly supported with respect to one another.

Another object of the instant invention is to provide such a contact block wherein the contact assembly is ductive contact member which is intended to engage a resistive track on the interior of a potentiometer casing, which conductive contact member is slidably received in the contact assembly to permit movement therein.

Yet another object of the instant invention is to provide such a contact block wherein the contact assembly is comprised of a plurality of wing-like sections each of which is comprised of a plurality of plate-like sections so arranged as to provide an internal channel for the reception of a movable conductive contact member.

Still another object of the instant invention is to pro vide such a contact block which makes possible the accurate phasing of conductive contact members thereof after the contact block is inserted in the cooperating potentiometer casing.

Yet another object of the instant invention is to proyide such a contact block which is of such shape and is so designed as to facilitate the gauging of a plurality thereof to produce a potentiometer having varied electrical characteristics.

Other objects and a fuller understanding of the instant invention may be had by referring to the following description and drawings, in which:

FIG. l is a schematic representation of a rotary potentiometer of a type designed to provide a sine and cosine output;

FIGS. 1A and 1B show sine and cosine outputs, respectively, which would appear at the outputs of the potentiometer of FIG. l;

FIG. 2 is a perspective view, partly in section, of a rotary contact block of the instant invention positioned in cooperative relationship with respect to a section of a potentiometer casing;

FIG. 3 is a cross-sectional view of a rotary potentiometer of the instant invention incorporating a plurality of the contact lblocks of FIG. 2;

FIGS. 4, 5 and 6 are plan views of plates utilizedin the construction of the contact block shown in FIGS. 2 and 3;

FIG. 7 is a cross-sectional view of the contact block of FIGS. 2 and 3 during a manufacturing stage thereof;

FIG. 8 is a detailed view of the conductive contact member utilized in the contact block and potentiometer of the instant invention; and

FIG. 9 is a plan view, partially in exploded perspective of the contact block of FIGS. 2 and 3 during a manufacturing stage thereof.

Referring specifically to FIG. l, there is shown in schematic form a rotary potentiometer 10 which, as well known in the art, includes a resistive track 12 on which a pair of contact arms 14 and 16 are movable in response to the rotation of a common shaft 18. The potentiometer illustrated in FIG. l is commonly known as a sine, cosine potentiometer since the waveforms 14 and 16' of FIGS. 1A and 1B, respectively, are generated at the outputs 20 and 22 thereof in response to a full revolution of the contact arms 14 and 16. As noted previously, the instant invention is broadly related to potentiometers of the type illustrated in FIG. l, but is more particularly concerned with the construction of rotary contact blocks therefor. Such contact blocks would customarily include those parts schematically illustrated as 14-20 in FIG. 1. Furthermore, it should be appreciated that although a sine, cosine potentiometer has been illustrated in FIGS. l, 1A and 1B, the instant invention is in no way dependent upon the particular output functions desired from a potentiometer constructed in accordance with the instant invention.

Turning to FIG. 2, there is shown a contact block 24 of the instant invention as it cooperates with one section 26 of the potentiometer 28, shown in cross-section in FIG. 3. The section 26 is of generally circular crosssection and includes an inwardly directed circular planar section 30 upon which is secured the resistive track 32, which would correspond to the resistive track 12 shown schematically in FIG. 1. Although not limited hereto, preferably the resistive track 32 is a conductive plastic material formed of a predetermined composition of conductive filler in an insulation resin (powder or liquid).

As best seen in FIG. 3, the contact block 24 is lixedly mounted on a shaft 34 by a set screw 36 engaging a V- shaped keyway 38 circumscribed in the shaft. The shaft 34 is rotatably mounted in conventional ball-'bearings 40 and 42 carried in end walls 44 and 46. It will be ap preciated that rotation of that portion of the shaft 34 fwhich extends beyond the end wall 44 will cause rotation of the contact block 24 therewith.

Contact block 24 includes a hub portion 47 of insulating material which, as will be explained in greater detail, is molded about a contact assembly broadly designated 48 in FIG. 2. Contact assembly 48 carries at least one conductive contact member 50 which, as best illustrated in FIG. 3, engages the resistive track 32 such as to correspond to the wiper arms 14 and 16 schematically shown in FIG. 1. As will be further explained, and as may be seen in FIGS. 2 and 3, an electrical circuit path is provided by a conductor 52 from each conductive contact member 50 to an individual Vshaped conductive ring 54 insulatingly mounted from one another by barriers 55 on one end of the hub 47. A pair of wire brushes 56 resides in the respective V-shaped rings and provide a circuit path to external terminals 58 which extend through the walls of section 26 into the interior of the potentiometer.

Overall operation is as follows. Assuming that only one conductive contact member 50 is being utilized, potential is applied to the resistive track 32 by way of external terminal 60, vertical pin 62, and a fine conductive strand 64. Although not seen in FIG. 2, other terminals 60 and their associated current paths may be provided in the manner shown, to permit the application of other potentials and/or to function as ground points for the potentiometer. Dependent upon the location of -the engagement of the conductive contact members 50 on the track 32, a predetermined portion of the potential which is applied at 60 will be transferred by the conductor 52, conductive ring 54 and the wire brushes 56 to the external terminal 58. By rotating the shaft 34, a waveform such as those shown in FIGS. 1A and 1B may be generated at the terminal 58.

Careful examination of the contact assembly 48 of the contact block 24 will reveal that the Contact assembly is actually comprised of a plurality of wing-like sections 66, 68, and 72 disposed in insulative relationship with respect to one another about the hub 47. In a manner to be further explained, wing-like section 72 carries conductive contact member 50', while if more than one conductive contact member is desired, as many as three more can be provided, one being carried by the winglike sections 66, 68, and 70. Furthermore, it will be appreciated that by reducing the size of each of the winglike sections 66, 68, 70, 72, it is possible to add more than the maximum of four which is possible with the invention illustrated.

Furthermore, it will be seen that each wing-like section is further comprised of a top plate section 74, a lower plate section 76 and an intermediate plate section 78 sandwiched therebetween. The intermediate plate 78 is of a smaller outside diameter than the plates 74 and 76, such as to leave the space 80 therebetween. Furthermore, and as seen best in FIGS. 2 and 9, the conductive contact member 50 includes a generally planar base portion 82 which is received within the space 80 defined between the plates 74 and 76.

As will be explained, during manufacturing of the potentiometer of the instant invention, and after the contact block 24 has been inserted within the casing, the conductive contact members such as 50 are movable from left to right and right to left as viewed in FIG. 9. It will be appreciated that the smaller diametered intermediate plate section 78 functions as an inner guide rail for the movement of the conductive contact member 50. Furthermore, it will be seen in FIG. 2 that the bottom plate section 76 includes a plurality of outstanding tab portions 84 which are overturned and overlap the upper plate sections 74. Thus the tabs 84 provide an outer guide rail for the base portion 82 of the conductive contact members 50. The plates 74, 76 and 78 are metallic and therefore provide a good, rm electrical path from the sandwiched conductive contact member 50 to the conductor 52 through which the potential taken off by the contact 50 is passed to the conductive V-rings 54.

As noted previously, FIG. 3 illustrates the overall assembly of the potentiometer 28 and particularly shows how two contact blocks 24 and 24 may be ganged on the shaft 34 and supported within the single casing. It may be appreciated that the contact block 24 is substantially identical to the contact block 24 but that certain parts have been removed for the sake of clarity. Thus the conductive contact members such as 50 are not shown on the conductive block 24 such that the space 80y where they reside is clearly seen defined by the intermediate plate 78 and the overlapped tab 84. FIG. 3 also illustrates the various combinations possible with the instant invention. Thus contact block 24 has four V-rings 54 and is thus designed for four conductive contact members 50, while contact block 24 has only two V-rings 54 signifying the use of two conductive contact members 50".

Sections 26 and 26 are suitably spaced between the end walls 44 and 46 by spacer rings 86 and 86 and the entire assembly is maintained by bolts 88 and nuts 90 passing through the respective sections. The spacing sleeve 92 and a biasing spring 94 position the shaft 34 within the interior of the potentiometer 28.

Turning to FIGS. 4-9, there is illustrated the novel method of manufacturing the contact block such as 24. Initially a metallic plate 96 is formed, preferably by stamping. Plate 96 includes a perimeter portion 98 which is detachably secured to the outer extremities of portions which would correspond to the tabs 84 shown in FIGS. 2 and 3. Furthermore, each pair of tabs 84 is an integral portion of inwardly directed plate section 76 which corresponds to the lower section 76 of each of the Wing-like sections 66, 68, 70 and 72 of FIG. 2. Furthermore, it will be appreciated that the inward extremities of each of the plate surfaces 76 are not connected to one another such that the integrity of the plate 96 is maintained in the initial stages by the perimeter portion 98.

Similarly, a second plate 100 is formed, preferably by stamping, and includes a detachable perimeter portion 102 and a plurality of inwardly directed plate sections 78 which correspond to the intermediate plate 78 shown in FIGS. 2, 3 and 9. As was for the case for the plate 96 in FIG. 4, it will be appreciated that the inward extremities of the plate sections 78 of the plate 100 are not connected to one another such that the integrity of the plate 100 is maintained during initial stages by the perimeter portion 102.

Finally, a third plate 104 of FIG. 6 is formed, preferably by stamping, and includes a perimeter portion 106 to which is detachably secured the plurality of inwardly directed plate sections 74 which correspond to the upper plate section 74 shown in FIGS. 2, 3 and 9. As was the case for the plates 96 and 100 of FIGS. 4 and 5, the sections 74 of FIG. 6 are not attached to one another but only to the removable perimeter section 106.

Next the three plates 96, 100 and 104 are supported in stacked relationship within a mold 108 shown in FIG. 7 with the plate 100 being sandwiched between the plates 96 and 106, as shown in the ligure. As illustrated best in FIG. 2, corresponding plate sections 74, 76 and 78 of the three plates are aligned, one above the other, such that when viewed from above in FIG. 2, only the top plate 74 of each wing-like section 66, 68, 70 and 72 is visible. It may be also noted that when in the assembled relationship of FIG. 7, each of the three perimeter portions 98, 102 and 106 of the respective plates is still secured to the respective plate sections of the plates. Next the insulating material which eventually forms the hub portion 47 of the contact block, is poured through the aperture 110 in the mold 108 such that the hub 47 is actually molded about the central portion of the various plate sections of the three plates.

After the hub 47 has hardened, the perimeter portions 98 and 106 of the plates 96 and 104, respectively, are cut away from their respective plate sections while the perimeter portion 102 of the plate 100 may be removed by initially snipping along the perforated lines 112 and then easily removing the perimeter portion 102 from the plate sections 78. It will be appreciated that upon the removal of the perimeter portion 102, there will be an empty space dened between each corresponding pair of plate sections 74, 76, which space has previously been identified as 80 and is shown also in FIG. 7.

It is to be further appreciated that once the perimeter portions 98, 102 and 106 have been removed from their respective plates, each of the sandwiched assemblies 66, 68, 70 and 72 comprising plate sections 74, 76 and 78 respectively, are individually and insulatingly supported with respect to one another in the molded hub 47.

As best illustrated in FIGS. 8 and 9, the next step in the manufacture of the contact block is to insert the conductive contact members 50 (as many as four may be used in the contact block illustrated in FIG. 9) into the spaces 80 dened in each Wing-like section. It will be seen in FIG. 9 that each contact member 50 includes the base portion 82 which has an inner diameter corresponding to the outer diameter of the plate sections 78 of the intermediate plate 100. Thus the outer diameter of each plate section 78 forms an inner guide rail for the base portion 82. of the respective contact member 50. With the base portion 82 abutting against the outer diameter of the plate section 78, the outstanding tabs 84 of each plate section 76 of plate 96 may then be folded over to overlap the outer plate section 74 to define an outer guide rail for the base portion 82 of the conductive contact members S0. It may be appreciated that by inserting a pointed instrument into the aperture 112 of the base portion 82 the entire contact member 50 may Ibe moved from left to right or right to left as viewed in FIG. 9.

Finally, the conductive rings 54, the insulating barriers 55, and the conductive wires S2 are added to the contact block and the entire contact block may be inserted within the potentiometer casing. As best seen in FIG. 3, the wire brushes 56 are spread apart and located in the V-rings 54.

At this time the conductive contact members 50 are in engagement with their respective tracks 32 shown in FIG. 2, and each sub-assembly such as the one shown in FIG. 2 may be electrically tested by connecting the potential sources to the terminals such as 60 and testing apparatus such as Oscilloscopes to the terminals such as 58. By rotating the shaft 34 the output wave appearing at 58 may be viewed on the scope. lf for some reason there is improper phasing between the various output waveforms, say for example, the waveforms of FIGS. lA and 1B were not exactly separated lby 90, then a pointed instrument would be inserted in the aperture 112 of the base portion 82 of the various conductive contact members 50 such that they could be physically displaced until the proper phasing is achieved. After the checker is satisfied, he would then permanently secure the conductive contact 50 in place, as by soldering.

It will be appreciated that the novel method described above makes possible the production of a plurality of insulatingly supported wing-like sections within which each conductive contact member may be physically moved to achieve proper phasing after the production of each contact block such that an accurately calibrated potentiometer is made possible in a simple and relatively inexpensive mode of manufacture.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A potentiometer comprising:

a casing;

first resistive means located internally of said casing;

a shaft rotatably mounted in said casing; and

a first contact block fixedly secured on said shaft, and

rotatable therewith, said rst contact block includ- 111g;

a hub portion of insulating material;

a contact assembly supported by said hub portion,

said Contact assembly carrying at least a first conductive contact member which engages said first resistive means;

first electrical circuit means completing an electrical circuit path from said conductive Contact member to a first terminal on the exterior of said casing;

second resistive means located internally of said casing, and a second contact block fixedly secured on said shaft and rotatable therewith, said second contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion,

said contact assembly including at least a first conductive contact member which engages said second resistive means; and

first electrical circuit means completing an electrical circuit path from said first conductive contact member to a second terminal on the exterior of said casing;

said cont-act assembly of said first contact block including a second conductive contact member which engages said first resistive means, said first and second conductive contacts being insulatingly maintained with respect to one another on said contact assembly of said first contact block; and further including second electrical circuit means on said first contact lblock completing an electrical circuit path from said second conductive contact member to a third terminal on the exterior of said casing;

wherein said first and third terminals extend through said casing, and said hub portion of said first contact block has first and second conductive rings fixedly mounted thereon and insulated one from another which are electrically connected to said first and second conductive contacts of said contact assembly of said first contact block, respectively, and further including first and second wire brush means associated with each of said first and second conductive contacts of said first contact block, respectively, one end of said first wire brush means connected to said first terminal, the opposite end of said first wire brush means being maintained in contact with said first conductive ring, one end of said second wire brush means connected to said third terminal means, the opposite end of said second wire brush means being maintained in contact with said second conductive ring, said first and second conductive rings together with their respective wire brush means forming portions of said first and second electrical circuit means of said first contact block.

2. A potentimeter comprising:

a casing;

first resistive means located internally of said casing;

a shaft rotatably mounted in said casing; and

a first contact block fixedly secured on said shaft, and rotatable therewith, said first contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion,

said contact assembly carrying at least a first conductive contact member which engages said first resistive means;

first electrical circuit means completing an electrical circuit path from said conductive contact member to a first terminal on the exterior of said casing;

second resistive means located internally of said casing, and a second contact block fixedly secured on said shaft and rotatable therewith, said second contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion,

said contact assembly including at least a rst conductive contact member which engages said second resistive means; and

first electrical circuit means completing an electrical circuit path from said first conductive contact member to a second terminal on the exterior of said casing;

said contact assembly of said first contact block including a second conductive contact member which engages said first resistive means, said first and second conductive contacts being insulatingly maintained with respect to one another one said contact assembly of said first contact block; and further including second electrical circuit means on said first contact block completing an electrical circuit path from said second conductive contact member to a third terminal on the exterior of said casing;

wherein said contact assembly of said first contact block includes a plurality of wing-like conductive sections insulatingly supported with respect to one another by said hub portion of said first contact block at predetermined spaced llocations thereabout, said first and second conductive contact members of said first contact block being secured to individual ones of said wing-like sections.

3. The potentiometer of claim 2, wherein said winglike sections of said contact assembly of said first Contact block each comprise a pair of spaced apart plate sections, said first and second conductive contact members of said first contact block including portions sandwiched between said pairs of plate sections of respective wing-like sections to assure firm electrical contact between said respective wing-like sections and their respective conductive Contact members.

4. A potentiometer comprising:

a casing;

first ressistive means located internally of said casing;

a shaft rotatably mounted in said casing; and

a first Contact block xedly secured on said shaft,

and rotatable therewith, said first contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion, said Contact assembly carrying at least a first conductive contact member which engages said first resistive means;

first electrical circuit means completing an electrical circuit path from said conductive contact member to a first terminal on the exterior of said casing;

second resistive means located internally of said casing, and a second Contact block fixedly secured on said shaft and rotatable therewith, said second contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion, said contact assembly including at least a first conductive contact member which engages said second resistive means; and

first electrical circuit means completing an electrical circuit path from said first conductive contact member to a second terminal on the exterior of said casing;

said contact assembly of said first contact block including a second conductive contact member which engages said first resistive means, said first and second conductive contacts being insulatingly maintained with respect to one another on said contact assembly of said first contact block; and further including second electrical circuit means on said first contact block completing an electrical circuit path from said second conductive contact member to a third terminal on the exterior of said casing;

wherein said first terminal extends into the interior of said casing, and said hub portion has a conductive ring mounted thereon which is electrically connected to said first conductive contact, said ring being rigidly secured to said hub portion and rotatable therewith; and further including wire brush means, one end of which is connected to said first terminal, the other end of said wire brush means being maintained in contact with said conductive ring, said conductive ring and said wire brush means forming a portion of said first electrical circuit means;

and further including second terminal means on the eX- terior of said casing and extending therethrough, said second terminal means being electrically connected to said first resistive means whereby potential applied to said second terminal may be applied to said first resistive means such that the magnitude of potential measured at said first terminal will be proportional to the magnitude of potential applied to said second terminal dependent upon the location of said first conductive contact member on said first resistive means;

wherein said contact assembly of said first contact block includes at least one wing-like conductive section, said first conductive contact member being secured to said wing-like section, said conductive ring being electrically connected to said wing-like section;

wherein said wing-like section comprises a pair of spaced apart plate sections, said first conductive contact member including a portion sandwiched between said pair of plate sections to assure firm electrical contact between said plate sections of said wing-like section and said conductive contact member.

5. A potentiometer comprising:

a casing;

first resistive means located internally of said casing;

a shaft rotatably mounted in said casing; and

a first Contact block fixedly secured on said shaft, and

rotatable therewith, said first contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion, said contact assembly carrying at least a first conductive contact member which engages said first resistive means;

first electrical circuit means completing an electrical circuit path from said conductive contact member to a first terminal on the exterior of said casing;

second resistive means located internally of said casing, and a second contact block fixedly secured on said shaft and rotatable therewith, said second contact block including;

a hub portion of insulating material;

a contact assembly supported by said hub portion, said contact assembly including at least a first conductive contact member which engages said second resistive means; and

first electrical circuit means completing an electrical circuit path from said first conductive contact mem* ber to a second terminal on the exterior of said casing;

said contact assembly of said first contact block including a second conductive contact member which engages said first resistive means, said first and second conductive contacts being insulatingly maintained with respect to one another on said contact assembly of said first contact block; and further including second electrical circuit means on said first contact block completing an electrical circuit path from said second conductive contact member to a third terminal on the exterior of said casing;

wherein said contact assembly of said first contact block includes at least one wing-like conductive section, said first conductive contact member being secured to said wing-like section;

wherein said wing-like section comprises a pair of spaced apart plate sections, said first conductive contact member including a portion sandwiched between said pair of plate sections to assure firm electrical contact between said plate sections of said wing-like section and said conductive contact member.

6. A contact block for use in a casing having resistive means located therein, said contact block comprising:

a hub portion;

a contact assembly including at least one wing-like section supported on said hub portion, said wing-like section including a pair of spaced apart plate sections provided with aligned notches;

a first conductive contact member slidably carried by said wing-like section and contacting said resistive means when said contact block is positioned within said casing, said first conductive member including an apertured portion slidably received within the aligned notches of said pair of spaced apart plate sections of said wing-like section;

a first conductive surface supported on said hub portion; and

first circuit means completing an electrical circuit path from said conductive contact member to said conductive surface;

whereby potential appearing at said first conductive contact member may be transferred to said first conductive surface.

7. The contact block of claim 6, wherein one of said pair of spaced apart plate sections includes underturned tab portions which overlap the other of said pair of spaced apart plate sections to define an outer guide rail for said portion of said first conductive contact member.

8. The contact block of claim 7, and further including a third plate section sandwiched between said pair of spaced apart plate sections, said third plate section being of smaller diameter than said pair of plate sections and thereby defining an inner guide rail for said portion of said first conductive contact member.

9. The contact block of claim 6, wherein said contact assembly includes a plurality of said wing-like sections insulatingly supported with respect to one another by said hub portion and disposed at predetermined locations thereabout; and further including a second conductive contact member slidably carried by a second one of said wing-like sections.

10. The contact block of claim 9, wherein each of said wing-like sections includes a pair of spaced apart plate sections and each of said rst and second contact members include a portion slidably received between a respective one of Said pairs of plate sections whereby said conductive contact members can be accurately positioned with respect to said resistive means when said contact block is positioned within said casing.

11. The contact block of claim 10, wherein one of each of said pair of spaced apart plate sections includes underturned tab portions which overlap the other of each of said pairs of spaced apart plate sections to dene outer guide rails for said portions of said irst and second conductive Contact members, respectively.

12. The contact block of claim 11, wherein each of said wing-like sections includes a third plate section sand- Wiched between the respective pairs of spaced apart plate sections, said third plate section being of smaller diameter than said respective pairs of spaced apart plate sections to define an inner guide rail for the movement of said portions of said first and second conductive contact members.

References Cited UNITED STATES PATENTS 2,859,319 11/1958 Karg 33S-199 X 2,806,928 9/1957 Wood et al 338-184X 3,303,453 2/1967 Doering 338-162 2,968,015 l/1961 Blanco 338-162 X 2,859,315 11/1958 Joerndt 338-130 FOREIGN PATENTS 1,017,345 1/ 1966 Great Britain.

LEWIS H. MYERS, Primary Examiner 20 A. T. GRIMLEY, Assistant Examiner U.S. C1. XR. 338-89, 171, 175 

